Ink transfer article for preparation of offset masters and method of making same andcomposition therefor



United States Patent() 3,138,477 INK TRANSFER ARTICLE FOR PREPARATION OF OFFSET MASTERS AND METHOD OF MAKING SAME AND COMPOSITION THEREFOR Stig A. Torstenson, Park Ridge, N.J., assignor t Burroughs Corporation, Detroit, Mich, a corporation of Michigan No Drawing. Filed Feb. 16, 1961, Ser. No. 89,616 9 Claims. (Cl. 11.7-36.1)

This invention relates generally to an ink transfer article, such as a typewriter ribbon, adapted for preparation of offset-printing master sheets, and to flexible master sheets which conveniently may be prepared by causing transfer of a pigment-carrying vehicle from the ink transfer article to the offset-printing surface of the master sheet.

To produce a small or moderate number of copies of printed matter, say from fewer than a hundred copies toa thousand or more copies, for example for oflice use, sales promotion purposes, and the type of printing shop operation in which a moderate number of copies of many different sheets of printed matter must be produced every week, it often is convenient to prepare offset-printing master sheets using a typewriter. These flexible master sheets then may be used in any number of commercially available duplicating machines of conventional design. In these machines an aqueous liquid is applied to the surface of the master sheet to render unrecep-tive to the offset-printing ink the portions of the surface free of printed matter, after which such an ink is applied to the master sheet surface, adheres only to the typed matter, and is transferred to a rubber blanket which then is brought into contact with a copy sheet.

To produce neat and legible copies by such a method it is necessary not only that the typed matter placed on the surface of the master sheet maintain its mechanical integrity through repeated assaults of the aqueous solution, but also that the exposed areas of the printed characters on the master sheet remain highly receptive to the offset-printing ink. In practice it is not uncommon to experience difliculty in obtaining good adherence of the offset-printing ink to all areas on the surface of a master sheet having the conformation of the copy matter which it is desired to print by offset-duplicating techniques. This difficulty is evidenced by light or spotty printed characters on the duplicate sheets. Such difficulties may be particularly persistent when it is attempted to prepare the flexible master sheet for offset printing by typing through a typewriter ribbon.

It is known that the copy matter placed on the offset master sheet surface must have a hydrophobic character and must be highly receptive to the oily vehicles of printing inks. Nevertheless, it has been found extraordinarily difficult in practice to obtain these properties in a ribbonimpregnating ink, which must include a pigment suitable for making legible typed matter and must utilize a nondrying vehicle which should not contain sizable quantities of waxy materials, since the presence of waxes or air-drying oils would impede migration from unused to used portions of the ribbon and result in short life in a typewriter. Experiments with numerous hydrophobic or water-repellent additives to the vehicles of conventional ribbon-impregnating inks have been made with generally unsatisfactory and unpredictable results. Factors other than water sensitivity appear to be involved.

Accordingly, it is an object of the present invention to provide an ink transfer article adapted for preparation of offset-printing master sheets, and a flexible master sheet for offset printing, which substantially avoid one or more of the disadvantages of the prior art arrangements.

It is also an object of this invention to provide a method of making ink transfer ribbons and a method of preparing a flexible master sheet for offset printing which likewise avoid one or more of the disadvantages of the prior art techniques.

It is a further object of the invention to provide a new and improved ink transfer article suitable for preparation of offset master sheets which, while having a long service life, will furnish not only typewritten material of the highest quality and legibility on ordinary paper, but also flexible master sheets for offset printing in which the typed copy matter on the master sheet surface remains coherent, adherent to the surface, and highly receptive to olfsetprinting inks during long runs of offset-printing cycles to produce many legible duplicate sheets from a single master.

A still further object of the invention is to provide a new and improved flexible master sheet for oifset printing, such master sheet carrying local deposits of pigments which are suitably bonded to the sheet surface and which maintain their mechanical integrity and high receptiveness to offset-printing inks during repeated printing cycles.

Yet another object of the invention is to provide a novel method of making ink transfer ribbons and preparing flexible master sheets therefrom which results in legible typed copy on the master sheet having substantially improved dependability and effectiveness in the prepara tion of duplicates by offset printing.

In accordance with the invention, an ink transfer article adapted for preparation of olfset-printing master sheets comprises a carrier member carrying pressure-transferable ink, the ink comprising dispersed pigment particles having surfaces to which is bonded a coordination complex compound of the type in which a trivalent metal is coordinated with an organic acid through its carboxylic oxygen atoms, this complex compound being selected from the group consisting of coordination complexes (a) of chromium and a fatty acid having between 10 and 20 carbon atoms, (b) of chromium and an acid in which the carboxyl radical is joined to an alpha, beta-unsaturated carbon chain having between 2 and 6 carbon atoms, and (c) of aluminum and myristic acid, whereby the pigment, bearing the complex compound, is adapted to be transferred by local pressure on the carrier to form, on a contiguous surface, visible local deposits highly receptive to offset-printing inks. As to be hereinafter described, the invention is preferably embodied in the form of a typewriter ribbon comprising a fibrous web impregnated with a nonvolatile, nondrying, liquid vehicle carrying the dispersed pigment.

In accordance with a feature of the invention, a flexible master sheet for olfset printing comprises a flexible base web having an offset-printing surface, and local deposits on the web surface highly receptive to offset-printing inks and having the conformation of the copy matter to be printed, these deposits being made up of a pigment the particles of which have surfaces to which is bonded a coordination complex compound of the aforementioned type, these complex-bearing pigment particles being made coherent and adherent to the master sheet web surface by a nonvolatile material bonding the pigment particles to each other and to the web surface.

In accordance with a method feature of the invention, ink transfer ribbons are made by the method comprising treating the particles of a pigment with a liquid material containing dissolved therein a coordination complex compound of the aforementioned type, removing the liquid material of the treating solution from the pigment by drying to leave the complex compound on the pigment particle surfaces, dispersing the treated pigment particles in a nonvolatile, nondrying liquid vehicle, and impregnating a fibrous ribbon wth the liquid vehicle containing the treated pigment in dispersion.

In accordance with a further method feature of the invention, a flexible master sheet for offset printing is prepared by a method comprising placing a fibrous web impregnated with a nonvolatile, nondrying liquid vehicle, containing the coordination complex-treated pigment in dispersion, in contact with a flexible blank offset master sheet and causing transfer by local pressure of the treated pigment in the vehicle from the web to the offset-printing surface of the master sheet to place thereon local, readily visible, adherent deposits unwet by aqueous liquids and having a high selective alfinity for offset-printing inks.

For a better understanding of the present invention, together with other and further objects thereof, reference is had to the following description, and its scope will be pointed out in the appended claims.

In carrying out the method of making ink transfer ribbons in accordance with the invention, particles of a pigment are treated with a liquid material containing dissolved therein a coordination complex compound of the type in which a trivalent metal is coordinated with an organic acid through its carboxylic oxygen atoms. These metal complex compounds commonly are described as Werner type complexes. T rivalent chromium is the most common metal used in forming such complex compounds available on the market, and fatty acids such as stearic acid and myristic acid will provide a coordination complex compound with trivalent chromium. The complex is to be distinguished sharply from the ordinary organic salts. For example, the salt chromium myristate, in which one trivalent chromium atom is combined with three acid groups CH (CH C(O)O, exists and is insoluble in water. In forming the more water-soluble Werner type chromium complex with the myristic group, however, the acid may be caused to combine with newly formed basic chromic dichloride, Cr(OH)Cl which may be viewed as (Cl )CrO(H). Two or more of these basic chromic chloride groups may be linked by coordinate bonds from the oxygen atom of one to the chromium atom of the next. One of the hydroxyl groups may combine with the carboxyl hydrogen of an acid molecule to split out H and link that chromium atom in the usual manner to the myristic acid, as if to form a trivalent chromium mixed salt, chromic dichloride monomyristate. The acyl oxygen of the carboxyl group is believed also to form a coordinate bond with the chromium atom in another basic chromium dichloride group, giving a complex containing at least two chromium atoms which may be represented as follows:

The complex as ordinarily obtained probably contains a mixture of such coordination complexes, some of which have only one Cl Cr group bonded to the carboxyl oxygen atoms, others of which have two chromium atoms as represented above, and still others of which have an additional Cr(Cl )-O(H)- group or groups between the carboxyl oxygen atoms. An average of about two chromium atoms, more or less, per acid group is preferred.

It will be understood by those skilled in the art that the above is intended merely as explanatory material to aid in distinguishing clearly between the well recognized Werner type coordination complex compounds and the simple salts of the metal and the organic acid. It is intended in this specification and in the appended claims to refer to these recognized metal-acid complexes without limitation to details of the exact arrangement of the coordinate and other bonds within the complex. Again, without limitation to exact structural arrangement for purposes of the present invention, it is understood that one of the two chlorine atoms in the complex compound may be separated from each chromium atom by ionization and the other chlorine atom replaced by a hydroxyl radical through partial hydrolysis, whereupon each chromium atom may become linked not only with a chromium atom in an adjacent complex molecule through Cr-OCr linkages, but also may become bonded through oxygen linkages with the surface of a pigment particle which is treated with the complex in aqueous solution. While the exact chemical mechanism of such treatment is not a part of the present invention, it will be understood that these Werner type complexes can be made to combine readily and quite firmly with the surfaces of the pigment particles.

The complex compound used in treating the pigment particles is selected from the group consisting of coordination complexes (a) of chromium and a fatty acid having between 10 and 20 carbon atoms, (b) of chromium and an acid in which the carboxyl radical is joined to an alpha, beta-unsaturated carbon chain having between 2 and 6 carbon atoms, and (c) of aluminum and myristic acid.

Excellent results have been obtained with the use of coordination complexes of chromium and the fatty acid myristic acid, C H COOH, or stearic acid, C H COOH, having 14 and 18 carbon atoms respectively and available on the market as Quilon M and Quilon S respectively. Other fatty acids whose complex compounds with chromium may be used alternatively are lauric acid, C H COOH; palmitic acid, C H COOH; and arachidie acid, C H COOH. Coordination complexes of chromium and the longer chain fatty acid cerotic acid, C H COOH, as well as the unsaturated acid oleic acid, C I-I COOH, are reported in the literature; while these may serve as rough equivalents, they cannot be expected to provide the desired properties to so great a degree as the previously mentioned fatty acid complexes.

Although aluminum has not been used to a great extent in forming coordination complexes with fatty acids, the coordination complex of aluminum and myristic acid now is available commercially and has been used in place of the corresponding chromium-myristic acid complex to treat the pigment with quite satisfactory results, although offset masters made from ribbons impregnated with a vehicle containing such pigment were somewhat less effective in providing many duplicates of the highest quality.

While the complexes with the fatty acids are preferred, quite acceptable and considerably improved impregnated ribbons and offset master sheets have been obtained using for the pigment treatment a complex compound of chromium and an acid in which the carboxyl radical is joined to an alpha, beta-unsaturated carbon chain having between 2 and 6 carbon atoms. Such an acid having 3 carbon atoms attached to the carboxyl radical is methacrylic acid, H C:C(CH )COOH, which forms a complex with trivalent chromium having a coordination bond arrangement with the carboxyl group of the acid which is believed to be identical with that illustrated above for the complex of chromium and myristic acid. Examples of other acids which may be used in place of the methacrylic acid are acrylic acid, H C:CH-COOH; crotonic acid, H CCH:CHCOOH; and sorbic acid,

The Werner type compound in which methacrylic acid is coordinated with chromium to form a complex which becomes well bonded to the surfaces of most treated pigments is available commercially as Volan bonding agent.

The treating of the pigment particles with a complex such as the chromium-myristic acid complex may be carried out as follows. This complex commonly is supplied as a 30% solution in isopropanol. One hundred parts of pigment may be dispersed in from about 3 to about 25 parts by weight of the isopropanol solution, to which roughly to parts of water conveniently may be added in order to get a free-flowing dispersion. Good results have been obtained using lithol red barium toner, identified in the Colour Index, Second Edition, by the number C.I. 15630; this pigment is the barium salt or lake of 2 (2 hydroxy 1 naphthylazo) l naphthalenesulfonic acid. One hundred parts of this pigment are mixed with 8 parts by weight of the 30% isopropanol solution of the chromium-myristic acid complex, diluted with 112 parts by weight of water. To this mixture are added 2.2 parts of an aqueous neutralizing or buffering solution containing 16.5% urea, 5.0% sodium formate, and 0.2% formic acid. This addition lowers the acidity of the treating solution and prevents an excessively acidic condition of the treated pigment and of the vehicle in which it is to be used. This particular neutralizing solution advantageously may be used in an amount by weight equal to between roughly a fourth and a third of the weight of the isopropanol solution. After obtaining good dispersion, for example in a dough mixer or similar apparatus, the temperature is raised to about 105 C. and held for a short period of time to assure hydrolysis of the complex and adequate bonding to the pigment surfaces, whereupon higher evaporating temperatures may be used to remove the liquid material of the treating solution from the pigment by drying to leave the complex compound on the dry pigment particle surfaces. Similar procedures may be followed in treating a pigment with any of the other complex compounds mentioned hereinabove. For example, the chromium-methacrylic acid complex is available as a 20% solution in a solvent of 40% isopropanol, 10% acetone, and 30% water. The aluminum-myristic acid complex also is available as a 20% solution in isopropanol and other solvents such as water and acetone. Further dilution with water or other solvent again may be made as convenient for treating the pigment.

When dispersed in a treating solution and dried as described, most of the complex compound is retained on the surfaces of the pigment particles. In the example given above, a weight of the complex equal to more than 2% of the weight of the pigment treated is retained by the pigment particles. A retention of about 1% to 5% of the weight of the pigment particles is recommended.

The dried treated pigment particles then are dispersed in a nonvolatile, nondrying liquid vehicle to form the ribbon-impregnating composition. The following composition in parts by weight represents a preferred ribboninking formulation:

Tricresyl phosphate 57.6 Castor oil 7.6 Oleic acid 3.8 Wetting agent 1.0 Complex-bearing lithol red 23.2 Channel black 6.8

The castor oil and oleic acid are nonvolatile, nondrying oils commonly used as the vehicle for ribbon-impregnating compositions. Alternative vehicle components might be sperm oil or certain mineral oil fractions giving a desired viscosity. Oily liquids such as tri(m-, p-)tolyl phosphate (the tricresyl phosphate of the above example) have proved to be quite valuable in these nonvolatile, nondrying vehicles. Any of numerous wetting agents, usually supplied in concentrated aqueous solution, for example the commonly available alkyl naphthalene sulfonates obtainable under the trade name Morcowet, may be used in roughly the indicated ratio to the vehicle or as necessary to facilitate dispersion of the pigment. The 23.2 parts of lithol red toner, treated as indicated above, contain approximately /2 part of the chromium-fatty acid (specifically, myristic acid) complex. The carbon black used is a free-flowing channel black obtainable under the trade name Peerless.

In formulating the composition given above, the lithol red and the channel black first may be mixed dry, then blended into the liquids carrying the wetting agent, followed by grinding on a three roll mill. Some of the tricresyl phosphate may be withheld at first to insure good milling and stirred in thereafter, if necessary with an additional pass through the mill. 'lihis ribbon-inking composition gives an acceptable red color. The channel black has the effect of somewhat dulling the red color and advantageously improves the absorption of infrared radiation by a character typed on ordinary paper from an impregnated ribbon, thus making it possible to obtain good duplicate copies of typed matter using heat sensitive duplicating systems. For this same purpose aluminum bronze (metallic aluminum) or other aluminum material may be used in place of part of the red pigment and carbon black. However, when the red pigment has been treated with the chromium coordination complex, it has been found that the desired results may be obtained, when an impregnated ribbon is used for typing offset masters, without having resorted to a similar treatment of the other pigment or pigments, present in smaller quantities in the ribbon-impregnating composition.

It will be understood that the constitution of the vehicle and the proportions of the pigments to the vehicle may be adjusted to get the desired flow and absorption characteristics of the ribbon-impregnating composition. Moreover, a wide variety of pigments is available to produce ribbon-inking compositions of red and other colors. For example, a carbon black may be the only pigment used to obtain a black ribbon-inking composition, in which case the carbon black is treated with the complex compound in a manner similar to the treatment of lithol red toner as described above. Some of the carbon black may be replaced by alkali blue paste (C.I. 42765), or the alkali blue pigment may be treated with the coordination complex and used without other pigments to obtain a blue ribbon. A number of other salts or lakes of sulfonic acid azo dyes are available as substitutes for the lithol red used in the composition set out above. One such pigment is the barium lake of Orange II, which is the barium salt of p-(2-hydroxy-l-naphthylazo)-benzenesulfonic acid (C.I. 15510). Another pigment red is the sodium salt or the barium lake of 6-(2-hydroxy-l-naphthylazo)-m-toluenesulfonic acid (C.I. 15590). Another useful red pigment is Norman Red Toner, identified in the Colour Index as C.I. Pigment Red 73. Among the inorganic pigments may be mentioned iron blue (Prussian blue, ferric ferrocyanide, C.I. 77510). Other inorganic pigments include ferroso-ferric oxide (magnetic black iron oxide, C.I. 77499) and cadmium yellow (cadmium sulfide, C.I. 77199). Any of these or other pigments or pigment mixtures may be used after treating all of the pigment or a substantial part thereof, preferably a major part by Weight, with one or more of the coordination complex compounds identified above. Some dye of suitable color also may be added to the ribbon-inking composition.

The pigments, including the treated pigment particles, are dispersed in a suitable manner, for example as outlined above, in the nonvolatile, nondrying liquid vehicle of the type illustrated in the formulation given above. A fibrous ribbons is impregnated with the liquid vehicle containing the treated pigment in dispersion. For the ribbonimpregnating operation, conventional apparatus such as the well known Haida ribbon-inking machine may be used, or inking arrangements as disclosed in Patents Nos. 2,766,717 and 2,833,242 to G. G. Neidich, E. M. Low, and H. A. Martin may be used. It will be understood that the term ribbon is used broadly for a web of any suitable length and width. The commonly used typewriter cotton fabric ribbon may be used for the fibrous ribbon, although other woven fibrous materials or fabrics such as nylon or silk may be used. The woven nature of the fabric using fibrous materials or threads provides the capillary interstices which permit heavy impregnation. Alternatively, a matted or felted fibrous web or paper may be used; paper typewriter ribbons may be impregnated or coated with substantial proportions of the ribboninking compositions to provide good transfer from the ribbon of the pigment-loaded vehicle over a substantial period of use.

The fibrous ribbon, when impregnated as described hereinabove, constitutes an ink transfer article adapted for preparation of offset-printing master sheets. It will be observed that this article comprises a fibrous web impregnated with a nonvolatile, nondrying liquid vehicle carrying a dispersed pigment, the particles of which have surfaces to which is bonded a coordination complex compound of the type defined hereinabove, whereby the treated complex-bearing pigment in the vehicle is adapted to be transferred by local pressure on the web to form on a contiguous surface visible local deposits highly receptive to offset-printing inks. In a preferred embodiment of such an ink transfer article and of the method of making it, the pigment is treated with an aqueous solution of a coordination complex compound in which trivalent chromium is coordinated with a fatty acid having between 10 and carbon atoms through the carboxylic oxygen atoms of the acid. A recommended form of such a coordination complex is a chromium complex with stearic acid or with myristic acid.

In carrying out the method embodying the present invention of preparing a flexible master sheet for offset printing, a fibrous web is impregnated with the liquid vehicle containing in dispersion the pigment treated with a complex compound as described hereinabove. The impregnated web then is placed in contact with a flexible blank offset-printing master sheet. This may be done by supplying or cutting the web in strip or ribbon form and inserting it in the usual manner as the ribbon in a typewriter, in which case the master sheet is run over the platen of the typewriter with the offset-printing surface of the master sheet facing the type bars. Upon typing in the usual manner, the local pressure or impact of the type, applied through the ribbon against the platen-supported master sheet while in contact with the ribbon on the typing line when the typewriter key is struck, causes transfer of the treated pigment in the nonvolatile vehicle from the web to the offset-printing surface to place thereon local, readily visible, adherent deposits unwet by aqueous liquids and having a high selective affinity for offset-printing inks.

This procedure produces a flexible master sheet for offset printing comprising a flexible base web having an offset-printing surface, and local deposits on this web surface highly receptive to offset-printing inks, and having the conformation of the copy matter to be printed, and specifically of the typed characters. These deposits accordingly are made up of the above-described pigment, most or all of the particles of which have surfaces to which is bonded the coordination complex compound of the type identified hereinabove. These complex-bearing pigment particles are made coherent and adherent to the web surface by the nonvolatile material of the vehicle bonding the pigment particles to each other and to the web surface. In the illustrative examples, these pigment particles are made coherent and adherent to the web surface by the nonvolatile, nondrying liquid of the vehicle. The vehicle wets the pigment particles and is partially absorbed into the absorptive offset-printing web surface of the master sheet, which conventionally has a fibrous fabric or paper structure permitting rapid entry of the vehicle into the capillary interstices near the surface of the web. Most of the pigment particles are too large to be drawn into the minute openings of the web surface and so remain as a deposit in the form of a legible character on the Web surface. However, the wetting action of the liquid vehicle upon the pigment particles maintains a sufficient portion of the vehicle in contact with the pigment particles (except possibly at and near the surface areas of the deposited pigment particles which are contacted by the offset-printing ink), thus effecting a bond with the surface of the web carrying the rest of the absorbed vehicle.

Thus the absorptive web surface permits fairly rapid drying of the material deposited on the surface of the master, thus minimizing smudging, while an adequate bond still is obtained between the contiguous portions of the vehicle near the web surface and on the pigment particles, so that the typed deposits will not chalk away after lengthy periods of time or suffer substantial erosion under the action of the cyclically applied aqueous bath and offsetprinting ink during repeated offset copying.

The present invention thus provides a reusable web or ribbon of cloth or paper, which may be used in place of conventional typewriter ribbons, having good shelf life and providing long service. Copy material typed or otherwise transferred with the use of such a ribbon not only provides printed matter of high quality and legibility for general communication and correspondence purposes, giving good performance in the usual office-duplicating equipments, but also gives transferred or type marks which, by virtue primarily of the complex-treated pigment, are unwet by aqueous liquids and have the high selective aflinity for printing inks which is needed for the preparation of good offset masters. These transferred or typed characters on offset master sheets withstand the mechanically disrupting forces exerted on the surfaces of the master sheet during repeated offset printing. Those prior art transfer ribbons which give adequate results for offset masters, as well as for ordinary correspondence, have in general resorted to vehicles high in waxy materials, which can be used only once and hence often use impenetrable films or plastic sheets as the base web. The transferred material depends on the waxes and oils of the ribbon-coating composition to get good results on offset masters. After passing once through the typewriter, the ribbon must be discarded. By virtue of the present invention, however, single or multi-colored cloth ribbons now may be used just as are the conventional typewriter ribbons, being unwound and rewound repeatedly on their spools, yet provide offset master sheets of excellent quality and utility.

While there have been described what at present are considered to be the preferred embodiments of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention. It is aimed, therefore, in the appended claims to cover all such changes and modifications which fall within the true spirit and scope of the invention.

What is claimed is:

1. An ink transfer article adapted for preparation of offset-printing master sheets, comprising: a fibrous web impregnated with a nonvolatile, nondrying liquid vehicle carrying a dispersed pigment, the particles of which have surfaces to which is bonded a coordination complex compound of the type in which a trivalent metal is coordinated with an organic acid through its carboxylic oxygen atoms, said complex compound being selected from the group consisting of coordination complexes (a) of chromium and a fatty acid having between 10 and 20 carbon atoms, (12) of chromium and an acid in which the carboxyl radical is joined to an alpha, beta-unsaturated carbon chain having between 2 and 6 carbon atoms, and (c) of aluminum and myristic acid, whereby said complex-bearing pigment in said vehicle is adapted to be transferred by local pressure on said fibrous web to form on a contiguous surface visible local deposits highly receptive to offset-printing inks.

2. An ink transfer article adapted for preparation of offset-printing master sheets, comprising: a fibrous web impregnated with a nonvolatile, nondrying liquid vehicle carrying a dispersed pigment, the particles of which have surfaces to which is bonded a coordination complex compound of the type in which trivalent chromium is coordinated with a fatty acid having between 10 and 20 carbon atoms through the carboxylic oxygen atoms of the acid, whereby said complex-bearing pigment in said vehicle is adapted to be transferred by local pressure on said fibrous Web to form on a contiguous surface visible local deposits highly receptive to offset-printing inks.

3. An ink transfer article, comprising: a fibrous web impregnated with a nonvolatile, nondrying liquid ribboninking vehicle carrying dispersed pigment particles which have surfaces treated with the coordination complex of chromium and stearic acid, whereby said complex-bearing pigment in the vehicle is adapted to be transferred by local pressure against the fibrous web to form on the surface of a contiguous offset-printing master sheet visible local deposits highly receptive to offset-printing inks.

4. An ink transfer article, comprising: a fibrous Web impregnated with a nonvolatile, nondrying liquid ribboninking vehicle carrying dispersed pigment particles which have surfaces treated with the coordination complex of chromium and myristic acid, whereby said complex-bearing pigment in the vehicle is adapted to be transferred by local pressure against the fibrous web to form on the surface of a contiguous offset-printing master sheet visible local deposits highly receptive to offset-printing inks.

5. The method of making ink transfer ribbons, comprising: treating the particles of a pigment with a liquid material containing dissolved therein a coordination complex compound of the type in which a trivalent metal is coordinated with an organic acid through its carboxylic oxygen atoms, said complex compound being selected from the group consisting of coordination complexes (at) of chromium and a fatty acid having between and 20 carbon atoms, (12) of chromium and an acid in which the carboxyl radical is joined to an alpha, beta-unsaturated carbon chain having between 2 and 6 carbon atoms, and (c) of aluminum and myristic acid; removing said liquid material of the treating solution from said pigment by drying to leave the complex compound on the pigment particle surfaces; dispersing the treated pigment particles in a nonvolatile, nondrying liquid vehicle; and impregnating a fibrous ribbon with said liquid vehicle containing said treated pigment in dispersion.

6. The method of making ink transfer ribbons, comprising: treating the particles of a pigment with a liquid material containing dissolved therein the coordination complex compound of chromium and stearic acid; removing said liquid material of the treating solution from said pigment by drying to leave the complex compound on the pigment particle surfaces; dispersing the treated pigment particles in a nonvolatile, nondrying liquid vehicle; and impregnating a fibrous ribbon with said liquid vehicle containing said treated pigment in dispersion.

7. The method of making ink transfer ribbons, comprising: treating the particles of a pigment with a liquid material containing dissolved therein the coordination complex compound of chromium and myristic acid; removing said liquid material of the treating solution from said pigment by drying to leave the complex compound on the pigment particle surfaces; dispersing the treated pigment particles in a nonvolatile, nondrying liquid vehicle; and impregnating a fibrous ribbon with said liquid vehicle containing said treated pigment in dispersion.

8. An article of the character described, comprising: a carrier member carrying pressure-transferable ink comprising a nonvolatile, nondrying liquid vehicle including dispersed pigment particles having surfaces to which is bonded a coordination complex compound of the type in which a trivalent metal is coordinated with an organic acid through its carboxylic oxygen atoms, said complex compound being selected from the group consisting of coordination complexes (a) of chromium and a fatty acid having between 10 and 20 carbon atoms, (22) of chromium and an acid in which the carboxyl radical is joined to an alpha, beta-unsaturated carbon chain having between 2 and 6 carbon atoms, and (c) of aluminum and myristic acid.

9. A liquid ink comprising particles of pigment dispersed in a nonvolatile liquid vehicle, said pigment particles having surfaces to which is bonded a coordination complex compound of the type in which a trivalent metal is coordinated with an organic acid through its carboxylic oxygen atoms, said complex compound being selected from the group consisting of coordination complexes (a) of chromium and a fatty acid having between 10 and 20 carbon atoms, ([1) of chromium and an acid in which the carboxyl radical is joined to an alpha, beta-unsaturated carbon chain having between 2 and 6 carbon atoms, and (c) of aluminum and myristic acid.

References Cited in the file of this patent UNITED STATES PATENTS 1,100,854 Tryon et al June 23, 1914 2,188,590 Bjorksten et al Jan. 30, 1940 2,273,040 Iler Feb. 17, 1942 2,545,125 Van Dusen Mar. 13, 1951 2,566,754 Van Dusen et al Sept. 4, 1951 2,729,575 Newman Jan. 3, 1956 2,764,085 Shoemaker et al Sept. 25, 1956 2,953,088 Newman Sept. 20, 1960 3,053,177 McI-lugh Sept. 11, 1962 

1. AN INK TRANSFER ARTICLE ADAPTED FOR PREPARATION OF OFFSET-PRINTING MASTER SHEETS, COMPRISING: A FIBROUS WEB IMPREGNATED WITH A NONVOLATILE, NONDRYING LIQUID VEHICLE CARRYING A DISPERSED PIGMENT, THE PARTICLES OF WHICH HAVE SURFACES TO WHICH IS BONDED A COORDINATION COMPLEX COMPOUND OF THE TYPE IN WHICH A TRIVALENT METAL IS COORDINATED WITH AN ORGANIC ACID THROUGH ITS CARBOXYLIC OXYGEN ATOMS, SAID COMPLEX COMPOUND BEING SELECTED FROM THE GROUP CONSISTING OF COORDINATION COMPLEXES (A) OF CHROMIUM AND A FATTY ACID HAVING BETWEEN 10 AND 20 CARBON ATOMS, (B) OF CHROMIUM AND AN ACID IN WHICH THE CARBOXYL RADICAL IS JOINED TO AN ALPHA, BETA-UNSATURATED CARBON CHAIN HAVING BETWEEN 2 AND 6 CARBON ATOMS, AND (C) OF ALUMINUM AND MYRISTIC ACID, WHEREBY SAID COMPLEX-BEARING PIGMENT IN SAID VEHICLE IS ADAPTED TO BE TRANSFERRED BY LOCAL PRESSURE ON SAID FIBROUS WEB TO FORM ON A CONTIGUOUS SURFACE VISIBLE LOCAL DEPOSITS HIGHLY RECEPTIVE TO OFFSET-PRINTING INKS. 